Vertical Turbine fire pump pulling from an open water source

[Schurtj]

I am interested in learning about vertical turbine fire pumps. I have a question. Say you have a vertical turbine fire pump to draft from an open wster source (lake) to support a sprinkler system. I wonder about potential clogging of the intake suction. Are these pumps able to reverse flow so that water can be pushed back through the strainer and screens? I feel like a reverse flow sequence would make maintenance easier. Also, how often should these screens be cleaned? I have heard horror stories of these pumps having to be removed, taken apart, and cleaned on a frequent basis. Thanks for the info and advice!

 

[Artisi]

A few points to consider :
1. The pump will only run maybe once a week or so for test run, therefore unlikely to see any blockage.
2.the system will(or should) have the system pressure maintained by a jacking pump, therefore the pump will only run for testing or when called on for a fire
3. The pump will drain back after each test run and flush the inlet.
4. The inlet strainer needs to be designed for minimum entry velocity, low velocity no blockage.
5.the pump should be able run in reverse, but check with manufacturer, but really not required as the water in the pump / discharge pipe work should be enough for flushing.


It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[TugboatEng]

Centrifugal pumps pump in the same direction regardless of shaft rotation direction.

 

[bimr]

Example of vertical turbine on a lagoon.

Example

Vertical Turbine

Pumping from a lake may be adequate fire system for an industrial application, but may be problematic for other applications because of the poor water quality. The water quality and potential plugging of the sprinklers will be a bigger issue than the fire pump.

 

[JJPellin]

We have several fire water pumps is this type of installation. It is a good idea to have piping set up so that water pressure can be directed to flow back down through the pump to flush out debris. We have not had much problem with this, but each water supply is going to be different. In cooling tower applications, we have dual screens on the path into the sump that can be pulled and cleaned on a running system without a need to pull the pump. Look up cooling tower screens.

Johnny Pellin

 

[TenPenny]

Here's an amusing tale that we ran into two years ago:

300 hp vertical turbine pump, 18" diameter, drawing fresh water from a lake, to a municipal water treatment plant. After the pump was running for some time, it was found that the flow delivered dropped by about 10%. After shut down (switching to the second pump), and being restarted the next day, everything was fine for a while, when it happened again. It was also found that this flow reduction usually happened at 1 to 2 am. The logical first step was to look at the operation of the plant, was there something going on overnight, or the operators in question? No, there wasn't.

Divers were hired with a submersible camera, pump was run until the flow dropped off, at which time divers sent down the camera, did an investigation, and found that the impeller eye was full of eels.

Apparently, the eels would move into the intake pumphouse when it was dark, and clog up the impeller, despite the intake screen on the pump. Discovered that the plant maintenance people had modified the other intake screens, with finer mesh, and nobody thought to mention this when they bought the new unit.

Moral of the story: make sure you know what is in the lake and what your pump might encounter.

 

[Artisi]

TenPenny: good story.


It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[LittleInch]

There's a few things here to consider.

1) what is the actual cleanliness requirement to allow a sprinkler system to operate without getting clogged?
2) How much space do you have and are these pumps just lowered in from a structure or??
3) You really need two sets of screens so you can clean one at a time without disabling the pump.
4) Size of the screen needs to be as big as you can get it
5) You are correct - there needs to be some means of measuring the DP when flowing to see if the screens need cleaning or not
6) To revers flow clean them you really need something which jets water at the screens not just a bit of backflow.
7) This is a very common issue so there are lots of equipment already made.

This lot use an air supply to blast air through for cleaning

https://www.hendrickcorp.com/screen/markets/water-intake-water-treatment/

or

https://www.rotorflush.com/

search "inlet screens raw water lake" or similar

The biggest issue is getting something that is certified for use on fire systems....


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Nutzman]

Be cautious with running vertical turbine pumps in reverse. Typically the driveshaft is threaded to be "ever tightening" in the direction of pumping. If you attempt to run in reverse the drive shaft couplings will "unscrew", driving the impellers into the bowl and twisting the drive shaft into the inter column "spider" bearings.
The thrust assembly normally comes with an anti-reverse rotation "ratchet", preventing reverse running.

 

[Artisi]

Nutzman, the line shafts won't unscrew if run in reverse from back flow, this is entirely different from being driven in reverse by wrong diver direction, this could / can / does unscrew couplings.
Anti rotation devices are fitted to stop reverse rotation as the pump could suffer critical speed problems if run for extended periods.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)